Like other Palestinian refugee camps in the Gaza Strip and the West Bank, Jabalya is widely seen as a stronghold for Palestinian national and Islamic groups.

Gaza's largest camp is also home to more than 100,000 Palestinians who live in poverty - their situation worsened by Israel's closure of Gaza, which has left most of them jobless.

As in other camps, such as Balata and Jenin in the West Bank, despair runs high, but so does a spirit of resistance.

On Monday night, Jabalya became the latest camp to be raided by Israeli tanks and helicopters in what Israel said was an operation to destroy "bases of terror" used to launch attacks against Israel.

While camp residents fled in panic, gunmen tried to fight off the Israeli tanks.

Among the 19 people who were killed, were four members of the Islamic militant group Hamas which has now vowed to retaliate.

Hard conditions

Established to shelter those left homeless after the creation of the state of Israel in 1948, Jabalya was home to a gunman who shot three Israelis dead in a suicide attack last week.

Jabalya refugee camp

Established after 1948 Arab-Israeli conflict

Area: 1.4 sq km

Population:101,605

Shelters: 40 sq m each maximum

His house was destroyed in Monday's raid, as was a metal workshop which Israeli officials said was used to make rockets and mortars.

Jabalya residents are no strangers to uprisings - it was here that the incident that sparked the first intifada in 1987 occurred.

And, observers say, the closure of Gaza by the Israeli authorities has led to an increased support for militant groups in the camp.

Most of the refugees here used to work as labourers on nearby Israeli farms. With the closure, they have lost their jobs.

Risa Qarra, public information officer for the UN's refugee office in Gaza, says there is about 70% unemployment in the camp.

The 1.4 square kilometre camp lacks basic infrastructure and extended families are often crammed into two or three small rooms.

The largest houses are 40 sq metres, packed closely together in narrow alleys often less than a metre wide.

West Bank militancy

The situation in the West Bank camps of Balata and Jenin - which have also been the scene of bloody Israeli incursions - is similar.

Many of the 19,000 Palestinians that call the Balata camp home still dream of returning to their family homes in Jaffa and other towns and villages along Israel's Mediterranean coastline.

Despair runs high in the refugee camps

Young Palestinians - the third generation since the Israeli state came into being - feel as strongly as their grandparents about their right to return. But, equally, they know it is a dream that can never be fulfilled.

Many of these youngsters were born into the camp and conditioned to militancy by the first Palestinian uprising.

Commentators say Balata, in particular, is a heartland of Hamas and Fatah radicals.

The sense of deprivation is very high, as is their sense of anger

Mustapha Barghouti

Posters lauding Palestinian suicide bombers as "martyrs" decorate the public walls, as does anti-Israeli graffiti.

Palestinian fighters are said to roam the streets freely carrying their M-16 rifles. And the Palestinian leader Yasser Arafat is said to be viewed by most as a distant figurehead.

The Israeli Government describes Balata and Jenin as "bases of terror" from where several suicide bombers have come.

Anger

Correspondents say these are areas where bombing operations are becoming increasingly popular with Palestinians frustrated by their conditions.

Armed militants freely roam the streets of Balata

A recent survey by the World Bank says that some 62% of Palestinians in the West Bank and Gaza live below the poverty line of $2 a day.

But, according to Dr Mustapha Barghouti, director of the Health Development Information and Policy Institute families in Balata are worse off than those in the poorest villages in Gaza.

Israeli travel restrictions have paralysed what little commerce there is left in the camps - adding to the sense of despair.

"The sense of deprivation is very high, as is their sense of anger," Mr Barghouti told BBC News Online.

Most of the people are unemployed and their housing conditions are desperate. There is a lack of basic facilities and open sewers, and in some cases, up to 15 people are forced to share two rooms in a house.

"This creates a terrible atmosphere," Mr Barghouti says.

The result, he says, is that support for the intifada is high.

Despite the incursions, there appears to be a sense of defiance on the streets, with young and old alike steadfastly refusing to leave their homes.